Photosubstitution of (fulvalene)tetracarbonyldiruthenium by alkenes and alkynes: First observation of alkyne coupling on fulvalene dimetals and synthesis of a (fulvalene)dimetallacyclopentadiene(alkene) complex

Irradiation (lambda(max) = 300-375 nm) of FvRu(2)(CO)(4) (1, Fv = eta(5): eta(5)-bicyclopentadienyl) or (mu(2)-eta(1):eta(5) -cyclopentadienyl)(2)Ru-2(CO)(4) (2) with dimethyl cis- or trans-butenedioate resulted in FvRu(2)(eta(2)-trans-CHR=CHR)(CO)(3) (3, R = CO2CH3). Prolonged irradiation of 1-3 provided FvRu(2)(eta(2)-trans-CHR=CHR)(2)(CO)(2)(4a, R = CO2CH3) and FvRu(2)(eta(2)-cis-CHR=CHR)(eta(2) -trans-CHR=CHR)(CO)(2) (4b, R = CO2CH3). Photocatalytic isomerization of cis to trans alkene occurred in the presence of 1-4. Irradiation of 1-3 with dimethyl butynedioate produced FvRu(2)(mu(2)-eta(2)-dimethyl butynedioate)(CO)(3) (5). Prolonged irradiation of 1-5 with the alkyne afforded FvRu(2)(mu(2)-eta(2):eta(4)-CRCRCRCR)(2)(CO) (6, R = CO2CH3). Irradiation of a THF solution of 6 generated FvRu(2)(mu(2)-eta(2):eta(4)-CRCRCRCR)(2)(THF) (7, R = CO2CH3). Photochemical alkyne cyclotrimerization was observed in the presence of 1-7. In the presence of CO, 7 reverted to 6 thermally. Heating 7 in the presence of dimethyl cis-butenedioate, thiophene, PPh3, or dimethyl sulfoxide (DMSO) afforded FvRu(2)(mu(2)-eta(2):eta(4)-CRCRCRCR)(2)(L) (8, R = CO2CH3, L = cis-CHR=CHR; 9, L = thiophene; 10, L = PPh3; 11, L = DMSO). Irradiation (300 nm) of a THF solution of 8, 9, or 11 provided 7, while 10 was inert. Thermal conversion of 8 to 10 or 11 was effected only at relatively high temperatures. Treatment of 9 with dimethyl cis-butenedioate, PPh3, or DMSO yielded 8, 10, and 11, respectively. Heating 11 at 210 degreesC in molten PPh3 afforded slowly 10. Kinetic experiments on the conversion of 9 to 10 point to dissociative substitution, E-a = 30.5 kcal mol(-1). Complexes 3-8 have been characterized by X-ray crystal analyses.